JP5138623B2 - Magnetic sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a magnetic sheet capable of reducing unnecessary electromagnetic waves emitted from an electronic device and suppressing electromagnetic interference caused by interference of unnecessary electromagnetic waves in the electronic device, and a low-cost and efficient manufacturing method thereof.

Applications of the magnetic sheet include noise suppression applications or RFID applications.
As the noise suppression application, along with the rapid progress of downsizing and higher frequency of electronic devices typified by personal computers and mobile phones, noise interference due to electromagnetic waves from outside and generated inside the electronic devices in these electronic devices In order to suppress interference between noises, various noise countermeasures have been taken. For example, a magnetic sheet (noise suppression sheet) is installed in the vicinity of a noise transmission source or reception source.

  The magnetic sheet is made of an alloy (magnetic powder) such as Fe-Si-Al, an epoxy resin, an acrylic resin, and a magnetic paint (magnetic sheet composition) containing a volatile solvent, such as PET or a PET film subjected to a release treatment. It is applied to the surface of an insulating support (base material), cured by a hot press and formed into a sheet shape, and the magnetic powder functions as a so-called noise suppressor that suppresses noise.

  On the other hand, as the RFID application, wireless communication using a coil antenna by an electromagnetic induction method has been widely used in recent years, as represented by a portable information terminal having an IC tag function called RFID (Radio Frequency Identification). Yes. For example, in portable information terminals, various conductors (metals) such as metal casings and metal parts are disposed in the vicinity of antenna elements for transmission and reception due to the miniaturization thereof. In this case, the presence of the metal in the vicinity of the antenna element greatly attenuates the magnetic field that can be used for communication, shortens the RFID communication distance in the electromagnetic induction method, and transmits and receives radio frequencies by shifting the resonance frequency. Can be difficult. Therefore, in order to suppress such electromagnetic interference, a magnetic sheet is disposed between the antenna element and the conductor.

  For example, when a magnetic sheet is used for a mobile phone, the magnetic sheet may be disposed at a battery pack site. However, as the battery pack expands due to repeated charging, the magnetic sheet may change in the direction of increasing thickness, and it adheres to the lid portion of the battery pack of the mobile phone, making it difficult to open and close the lid. There is. Further, when the thickness is increased, the binder may not be able to hold the magnetic powder, and powder may fall off. Furthermore, when the lid is opened and closed, there is a problem that the magnetic sheet is rubbed and powdered off.

On the other hand, in recent years, a magnetic sheet has been proposed in which an insulating support is bonded to the surface of a magnetic layer with an adhesive. When this magnetic sheet is used, the insulating support can be interposed between the lid of the battery pack and the magnetic layer. Therefore, even if the magnetic layer expands due to heat, the insulating support can be separated. This prevents adhesion between the battery pack lid and the magnetic layer and improves the problem of the lid opening / closing failure.
For this reason, many magnetic sheets having a structure in which a magnetic layer and an insulating support are bonded using an adhesive or an adhesive have been proposed (see Patent Documents 1 to 4).

However, since any of these magnetic sheets uses a pressure-sensitive adhesive or an adhesive, the magnetic sheet (magnetic layer) must be thinned by the thickness of the pressure-sensitive adhesive or the adhesive. Furthermore, when the inside of the electronic device is heated, an adhesive or the like may leak into the electronic device, which may cause a failure of the electronic device.
In addition, in a magnetic sheet obtained by bonding a magnetic layer and an insulating support with an adhesive or the like, in the production process, first, a magnetic sheet is prepared by curing by hot pressing or the like, and the adhesive layer is formed on the magnetic sheet. In addition, it is necessary to laminate an insulating support thereon. For this reason, there are problems that the manufacturing process is complicated and the cost is increased. In addition, the insulating support also has a problem that scratches are generated by opening and closing the lid and the appearance is deteriorated.

Moreover, since the said magnetic sheet is integrated in an electronic device etc., it is requested | required to have heat resistance and a flame retardance, and generally adding a flame retardant is performed.
As conventional flame retardants, halogen compounds such as brominated flame retardants are mainly used, and when these halogen compounds burn, they generate harmful substances typified by environmental hormones. The load on the environment is large, and its use is decreasing.
However, when a halogen-free flame retardant is used, usually sufficient flame retardancy cannot be exhibited unless a large amount of flame retardant is added. However, when a large amount of flame retardant is added, the magnetic permeability decreases. In addition, the magnetic sheet may become hard. As halogen-free flame retardants, phosphorus is generally used in many cases, and it has been difficult to exhibit sufficient flame retardancy without containing phosphorus.

  Therefore, without using an adhesive between the magnetic layer and the insulating support, a simple and low-cost method for producing a magnetic sheet efficiently, and without an adhesive layer, the surface slipperiness is good. Thus, it is desired to develop a magnetic sheet that has sufficient flame retardancy even when the amount of the flame retardant used is small and exhibits an excellent noise suppression effect.

JP 2007-165701 A JP 2007-123373 A JP 2006-301900 A JP 2001-329234 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention can reduce unnecessary electromagnetic waves emitted from electronic devices and suppress electromagnetic interference caused by interference of unnecessary electromagnetic waves in electronic devices, has excellent surface slipperiness, high flame retardancy, and noise suppression. An object of the present invention is to provide a magnetic sheet having an effect and having a small environmental load, and a simple, low-cost and efficient manufacturing method thereof.

Means for solving the problems are as follows. That is,
<1> It has a magnetic layer and a concavo-convex forming layer,
The magnetic layer contains at least a binder, magnetic powder, and a flame retardant, and the flame retardant contains at least one of melamine cyanurate containing silicon atoms and melamine cyanurate containing carboxylic acid amide,
The unevenness forming layer is a magnetic sheet having flame retardancy and Beck smoothness of 20 seconds / mL or less.
In the magnetic sheet according to <1>, since the Beck smoothness of the unevenness forming layer is as low as 20 seconds / mL or less, the surface of the unevenness forming layer is excellent in slipperiness. Even when the battery pack is stored around the battery pack, it is possible to suppress the occurrence of a lid opening / closing failure without adhering to the battery pack lid. In addition, the magnetic sheet does not have an adhesive layer made of an adhesive or the like, and is composed of the magnetic layer and the concavo-convex forming layer. Therefore, the adhesive produced when used at a high temperature in an electronic device. Occurrence of failure of the electronic device due to the leakage of the agent is prevented. In the magnetic sheet of the present invention, the unevenness forming layer has flame retardancy, and the magnetic layer contains melamine cyanurate containing silicon atoms and melamine shear containing the carboxylic acid amide as the flame retardant. Since it contains at least one of nurate, it has high flame retardancy, can suppress the falling of magnetic powder, is halogen-free, and has a low environmental burden.
<2> The magnetic layer contains 700 parts by mass to 1,300 parts by mass of magnetic powder, 35 parts by mass to 100 parts by mass of a flame retardant, and 100% by mass of the magnetic powder in the magnetic layer with respect to 100 parts by mass of the binder. Is the magnetic sheet according to <1>, wherein the content of is from 70 wt% to 90 wt%.
<3> The magnetic sheet according to any one of <1> to <2>, further including carbon fiber in the magnetic layer.
<4> The magnetic sheet according to any one of <1> to <3>, wherein the melamine cyanurate containing a silicon atom and the melamine cyanurate containing a carboxylic acid amide have a number average particle diameter of 1 μm or less.
In the magnetic sheet according to <4>, since the number average particle diameter of the melamine cyanurate is as small as 1 μm or less, a flame retardant having a large particle diameter is prevented without inhibiting the magnetic powder from being closely oriented. High magnetic permeability can be obtained as compared with the case of using.
<5> The magnetic sheet according to any one of <1> to <4>, wherein the flame retardant further includes red phosphorus.
<6> The magnetic sheet according to <5>, wherein the magnetic layer includes 6 to 20 parts by mass of red phosphorus with respect to 100 parts by mass of the binder.
<7> The magnetic sheet according to any one of <1> to <6>, further including a curing agent in the magnetic layer.
In the magnetic sheet according to <7>, since the hardener is further included in the magnetic layer, a change in the thickness of the magnetic sheet under a high temperature and high humidity environment can be reduced.
<8> The magnetic sheet according to <7>, wherein the binder contains at least one of an epoxy resin and an acrylic resin.
In the magnetic sheet according to <8>, since the binder contains at least one of an epoxy resin and an acrylic resin, a change in the thickness of the magnetic sheet under a high temperature and high humidity environment can be reduced.
<9> The magnetic sheet according to any one of <1> to <8>, wherein the magnetic layer has a thickness of 25 to 500 μm.
<10> The magnetic sheet according to any one of <1> to <9>, which is used as a noise suppressor.

<11> A magnetic layer forming step of forming a magnetic layer by molding a magnetic composition prepared by adding magnetic powder and a flame retardant to a binder;
After the concave / convex forming layer and the transfer material are stacked in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer, the surface shape of the transfer material is changed to the concave / convex forming layer by heat pressing. And transferring to the surface of the magnetic layer, and a shape transfer step of joining the unevenness forming layer and the magnetic layer;
Is a method for producing a magnetic sheet, comprising:
In the method for producing a magnetic sheet according to <11>, in the magnetic layer forming step, the magnetic composition prepared by adding the magnetic powder and the flame retardant to the binder is molded to form the magnetic sheet. A layer is formed. In the shape transfer step, the unevenness forming layer and the transfer material are stacked and arranged in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer, and then heated and pressed. The surface shape of the transfer material is transferred to the surface of the concavo-convex forming layer and the magnetic layer, and the concavo-convex forming layer and the magnetic layer are directly joined without using an adhesive or the like. As a result, a magnetic sheet can be obtained simply and efficiently at low cost.
In the obtained magnetic sheet, since the surface shape of the transfer material is transferred to the surface of the concavo-convex forming layer, the surface of the concavo-convex forming layer is roughened, the Beck smoothness is low, and the slip Excellent in properties.
<12> The method for producing a magnetic sheet according to <11>, wherein the binder includes at least a thermosetting organic resin, and the thermosetting organic resin before hot pressing is in an uncured state.
<13> Any one of <11> to <12>, wherein the shape transfer step includes laminating a release layer and a transfer material in this order from the magnetic layer side on the other surface in the thickness direction of the magnetic layer. It is a manufacturing method of the magnetic sheet as described in above.
<14> The method for producing a magnetic sheet according to any one of <11> to <13>, wherein the transfer material has irregularities on the surface.
<15> The method for producing a magnetic sheet according to any one of <12> to <14>, wherein the surface of the concavo-convex forming layer is subjected to either a matting treatment or a peeling treatment without using a silicone resin.
<16> The method for producing a magnetic sheet according to any one of <11> to <15>, wherein the Beck smoothness of the unevenness forming layer before hot pressing is 200 seconds / mL or less.
<17> The method for producing a magnetic sheet according to any one of <11> to <16>, wherein the Beck smoothness of the concavo-convex forming layer after hot pressing is 20 seconds / mL or less.

  According to the present invention, it is possible to solve the above-mentioned problems in the past, reduce unnecessary electromagnetic waves emitted from electronic devices, and suppress electromagnetic interference caused by interference of unnecessary electromagnetic waves in electronic devices, and have excellent surface slipperiness. Further, it is possible to provide a magnetic sheet having high flame retardancy and noise suppressing effect and having a small environmental load, and a simple, low-cost and efficient manufacturing method thereof.

FIG. 1A is a process diagram (part 1) illustrating an example of a method for producing a magnetic sheet of the present invention. FIG. 1B is a process diagram (part 2) illustrating an example of the method for producing a magnetic sheet of the present invention. FIG. 1C is a process diagram (part 3) showing an example of the method for producing a magnetic sheet of the present invention, and shows an example of the obtained magnetic sheet (the present invention). 2A is a graph showing Py-GC-MS measurement data of the flame retardant (MC-5F) used in Example 1. FIG. FIG. 2B is a graph showing Py-GC-MS measurement data of melamine cyanurate without surface treatment (MC-20N) for the purpose of comparison with FIG. 2A. FIG. 2C is a graph showing Py-GC-MS measurement data of melamine cyanurate without surface treatment (MC-40N) for the purpose of comparison with FIG. 2A. FIG. 3A is a graph showing IR measurement data of a concentrate of a magnetic powder toluene cleaning solution. FIG. 3B is a graph showing a match result in a library search between a concentrate of a magnetic powder toluene washing solution and a glyceride. 4A is a graph showing XRF measurement data of the flame retardant (MC-5S) used in Example 6. FIG. FIG. 4B is a graph showing XRF measurement data of melamine cyanurate without surface treatment (MC-20N) for the purpose of comparison with FIG. 4A. FIG. 4C is a graph showing XRF measurement data of melamine cyanurate without surface treatment (MC-40N) for the purpose of comparison with FIG. 4A. FIG. 5 is a diagram for explaining a transmission loss measurement method.

(Magnetic sheet)
The magnetic sheet of the present invention comprises a magnetic layer and a concavo-convex forming layer.

-Magnetic layer-
The magnetic layer has functions of reducing unnecessary electromagnetic waves emitted from the electronic device and suppressing electromagnetic interference caused by interference of unnecessary electromagnetic waves in the electronic device.
The magnetic layer contains at least a binder, magnetic powder, and a flame retardant, preferably contains carbon fiber, and further contains other components appropriately selected as necessary.

--Binder--
The binder is not particularly limited and may be appropriately selected depending on the intended purpose, but preferably contains at least a thermosetting organic resin, for example, an acrylic resin containing a thermosetting organic resin is preferred. Can be mentioned.

There is no restriction | limiting in particular as said thermosetting organic resin, Although it can select suitably according to the objective, For example, an epoxy resin is mentioned suitably. When an epoxy resin having a low molecular weight is added, the melt viscosity of the binder is further lowered when the magnetic sheet is compressed (molded), so that the magnetic properties can be improved. For example, a polyfunctional epoxy resin can be used. If it uses, the reliability of the magnetic sheet after hardening can be improved more.
Examples of the epoxy resin include an anion curing epoxy resin using a microencapsulated amine curing agent, a cation curing epoxy resin using an onium salt, a sulfonium salt, and the like as a curing agent, and an organic peroxide as a curing agent. Preferred examples include the radical curable epoxy resin used. These may be used individually by 1 type and may use 2 or more types together.

Furthermore, the binder containing the epoxy resin preferably contains a latent curing agent as the curing agent for the epoxy resin.
The latent curing agent means one that exhibits the function of a curing agent at a specific temperature. Examples of the curing agent include amines, phenols, acid anhydrides, imidazoles, dicyandiamide, and isocyanate. And the like.

The acrylic resin preferably has an epoxy group. In this case, for example, when used together with an aluminum chelate-based curing agent, the epoxy group and the aluminum chelate-based curing agent react with each other, thereby improving the reliability.
The acrylic resin preferably further has a hydroxyl group. Adhesiveness can be improved by having this hydroxyl group.
There is no restriction | limiting in particular as a weight average molecular weight of the said acrylic resin, Although it can select suitably according to the objective, 10,000-850,000 are preferable at the point which is excellent in applicability | paintability.
When the weight average molecular weight is less than 10,000, the viscosity of the magnetic composition (prepared by adding the magnetic powder, the flame retardant, etc. to the binder) is reduced, and a magnetic powder having a large weight is used. It may be difficult to apply, and if it exceeds 850,000, the viscosity of the magnetic composition may increase, and it may be difficult to apply.
The glass transition temperature of the acrylic resin is preferably −50 ° C. to + 15 ° C. from the viewpoint of reliability.
When the glass transition temperature is less than −50 ° C., the reliability in a high temperature or high temperature and high humidity environment may deteriorate, and when it exceeds + 15 ° C., the magnetic sheet tends to be hard.

--- Magnetic powder--
There is no restriction | limiting in particular as said magnetic powder, According to the objective, it can select suitably, For example, flat shape, lump shape, fibrous shape, spherical shape, indefinite shape etc. are mentioned. Among these, the flat shape is preferable in that the magnetic powder can be easily oriented in a predetermined direction and the magnetic permeability can be increased.
Examples of the magnetic powder include soft magnetic metal, ferrite, and pure iron particles.
Examples of the soft magnetic metal include magnetic stainless steel (Fe—Cr—Al—Si alloy), sendust (Fe—Si—Al alloy), permalloy (Fe—Ni alloy), and silicon copper (Fe—Cu—Si alloy). Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-Ni-Cr-Si alloy, Fe-Si-Cr alloy, Fe-Si-Al-Ni-Cr alloy, and the like.
Examples of the ferrite include Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Mn ferrite, Cu-Zn ferrite, soft ferrite such as Cu-Mg-Zn ferrite, and hard ferrite that is a permanent magnet material. Can be mentioned.
The said magnetic powder may be used individually by 1 type, and may use 2 or more types together.

--Flame retardant--
By adding the flame retardant, the flame retardancy of the magnetic sheet can be improved.
In the magnetic sheet of the present invention, the flame retardant contains at least one of melamine cyanurate containing silicon atoms and melamine cyanurate containing carboxylic acid amide.
As a conventional flame retardant, a halogen-based compound is mainly used, but there is a problem that when it burns, a harmful substance is generated and the burden on the environment is large. Further, as a halogen-free flame retardant, for example, melamine cyanurate that is not subjected to any surface treatment is known, but the melamine cyanurate has poor affinity with the binder and is difficult to disperse in the binder. In the case of intending to obtain a hard magnetic sheet, there is a problem that the mechanical strength of the magnetic sheet immediately after molding (pressing) is reduced (softened). Moreover, since mechanical strength falls significantly, it is difficult to increase the addition amount of the said melamine cyanurate, and sufficient flame retardance cannot be obtained. Furthermore, so-called “powder-off” is likely to occur from the surface of the magnetic sheet.

  Here, the melamine cyanurate is a melamine isocyanurate adduct, and melamine and isocyanurate are formed as an oligomer adduct by repeating an addition reaction as shown in the following reaction formula. It is.

The melamine cyanurate has rigidity due to a melamine skeleton, and a hydroxyl group (OH) is generated by the addition reaction. Therefore, the melamine cyanurate is considered to exhibit flame retardancy by having a polarity due to the hydroxyl group. However, the hydroxyl group often forms a hydrogen bond between molecules, and it is presumed that the hydrogen bond by the hydroxyl group causes the isocyanurate aggregation. Therefore, it is considered that the occurrence of aggregation is suppressed and the dispersibility in the binder is improved by blocking this hydrogen bond, that is, by using melamine cyanurate in which some hydroxyl groups are protected.
Therefore, as the flame retardant, melamine cyanurate containing silicon atoms (melamine cyanurate surface-treated with a silicon compound) and melamine cyanurate containing carboxylic acid amide (melamine cyanurate surface-treated with a fatty acid) When at least one of the above is used, higher flame retardancy is exhibited as compared to melamine cyanurate (not surface-treated), and it is difficult for powder to fall off from the surface of the magnetic sheet. For example, when the acrylic resin is used, it is found that a magnetic sheet with good surface smoothness can be obtained in which the curing of the binder during pressing is accelerated and the change in thickness under a high temperature and high humidity environment is suppressed. It was.
Further, as a result of examining the particle size of the flame retardant, for example, in the case of melamine cyanurate containing silicon atoms, when the average particle size is larger than 1 μm, the thickness change of the magnetic sheet may be increased, It has been found that the characteristics may also deteriorate. It was also found that flame retardants other than melamine cyanurate containing either a silicon atom or a carboxylic acid amide cannot obtain sufficient flame retardancy even when one having an average particle size of 1 μm or less is used. In addition, when melamine cyanurate that has not been surface-treated is used, air enters the magnetic sheet, so that powder falls off easily, and it was found that sufficient flame retardancy cannot be obtained with a small addition amount. .

[Melamine cyanurate containing silicon atoms]
The presence of the silicon atom in the melamine cyanurate containing the silicon atom can be confirmed by, for example, fluorescent X-ray analysis (XRF).

There is no restriction | limiting in particular as a number average particle diameter of the said melamine cyanurate containing a silicon atom, Although it can select suitably according to the objective, 1 micrometer or less is preferable.
When the number average particle diameter exceeds 1 μm, the magnetic powder may be prevented from being densely oriented and the magnetic properties of the magnetic sheet may be deteriorated, and the thickness change under high temperature or high temperature and high humidity environment is large. May be.
The number average particle diameter can be measured from, for example, a particle size distribution measured using laser diffraction.

The melamine cyanurate containing a silicon atom may be a commercially available product or may be appropriately prepared.
As said commercial item, MC-5S (made by Sakai Chemical Industry) etc. are mentioned, for example.
The method for producing the melamine cyanurate containing silicon atoms is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a method of surface-treating melamine cyanurate using a silicon compound is preferable. It is done.
There is no restriction | limiting in particular as the method of the said surface treatment, It can select suitably from well-known methods, For example, the method of mixing and stirring the said melamine cyanurate and the said silicon compound is mentioned.

  There is no restriction | limiting in particular as said silicon compound, According to the objective, it can select suitably, For example, organopolysiloxanes, such as methyl hydrogen polysiloxane, dimethyl polysiloxane, and methylphenyl polysiloxane; Methyl trimethoxysilane, ethyl Trimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octadecyltrimethoxysilane, dimethyldimethoxysilane, octyltriethoxysilane, trifluoromethylethyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, vinyl And silane compounds containing a silane coupling agent such as trimethoxysilane and γ-aminopropyltrimethoxysilane. These may be used individually by 1 type and may use 2 or more types together. Among these, alkoxysilanes such as methyltrimethoxysilane and ethyltrimethoxysilane are preferable in terms of good reactivity.

[Melamine cyanurate containing carboxylic acid amide]
The presence of the carboxylic acid amide in the melamine cyanurate containing the carboxylic acid amide can be confirmed using, for example, pyrolysis gas chromatography (Py-GC-MS).

There is no restriction | limiting in particular as a number average particle diameter of the melamine cyanurate containing the said carboxylic acid amide, Although it can select suitably according to the objective, 1 micrometer or less is preferable.
When the number average particle diameter exceeds 1 μm, the magnetic powder may be prevented from being densely oriented and the magnetic properties of the magnetic sheet may be deteriorated, and the thickness change under high temperature or high temperature and high humidity environment is large. May be.
The number average particle diameter can be measured from, for example, a particle size distribution measured using laser diffraction.

The melamine cyanurate containing the carboxylic acid amide may be a commercially available product or an appropriately prepared product.
As said commercial item, MC-5F (made by Sakai Chemical Industry) etc. are mentioned, for example.
A method for producing the melamine cyanurate containing the carboxylic acid amide is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a method of surface-treating melamine cyanurate using a fatty acid is preferable. It is done.

There is no restriction | limiting in particular as the method of the said surface treatment, It can select suitably from well-known methods, For example, the method of mixing and stirring the said melamine cyanurate and the said fatty acid is mentioned.
When the melamine cyanurate is surface-treated using the fatty acid, the amino group in the melamine cyanurate reacts with the fatty acid to be converted into an amide compound as shown in the following formula (1). it is conceivable that. For this reason, if it analyzes using the said pyrolysis gas chromatography (Py-GC-MS), presence of the said carboxylic acid amide can be confirmed.
—NH ₂ + R—COOH → R—CONH— Formula (1)

  The fatty acid is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include lauric acid, isostearic acid, stearic acid, palmitic acid, oleic acid, and linolenic acid. These may be used individually by 1 type and may use 2 or more types together. Among these, lauric acid is preferable in terms of high hydrophobicity and good dispersibility.

[Red phosphorus]
The flame retardant may further contain red phosphorus in addition to the melamine cyanurate containing silicon atoms and the melamine cyanurate containing the carboxylic acid amide. In this case, the flame retardancy of the magnetic sheet can be further improved.
The red phosphorus is not particularly limited and may be a commercially available product or an appropriately synthesized product, but has excellent moisture resistance, does not spontaneously ignite when mixed, and has good safety. The surface is preferably coated.
Examples of the red phosphorus coated on the surface include those obtained by surface-treating the surface of red phosphorus with aluminum hydroxide.

There is no restriction | limiting in particular as content of the said red phosphorus, Although it can select suitably according to the objective, 6-20 mass parts is preferable with respect to 100 mass parts of said binders.
When the content is less than 6 parts by mass, the effect of improving flame retardancy may not be obtained. When the content exceeds 20 parts by mass, the total amount of the magnetic powder and the flame retardant with respect to the binder increases. In addition to making it difficult to hold the magnetic powder and the flame retardant together with the binder, the content ratio of the magnetic powder in the magnetic sheet may be reduced, and the magnetic permeability may be reduced.
In addition, by adjusting the blending ratio of the red phosphorus, the melamine cyanurate containing silicon atoms and the melamine cyanurate containing carboxylic acid amide, both high flame retardancy and suppression of powder falling off of the magnetic powder are achieved. can do.

  The content of the binder, the magnetic powder, and the flame retardant (at least one of the melamine cyanurate containing silicon atoms and the melamine cyanurate containing carboxylic acid amide) is not particularly limited, and is appropriately determined depending on the purpose. The magnetic powder is 700 to 1,300 parts by mass with respect to 100 parts by mass of the binder, and at least of the melamine cyanurate including the silicon atom and the melamine cyanurate including the carboxylic acid amide. It is preferable that either (a silicon atom and a carboxylic acid amide are used in combination) is 35 to 100 parts by mass.

  When the content of the magnetic powder is less than 700 parts by mass, excellent magnetic properties may not be obtained. When the content exceeds 1,300 parts by mass, the magnetic powder is held together with the binder. In a high-temperature and high-humidity environment, the thickness change of the magnetic sheet becomes large, the flame retardant may bleed on the surface of the magnetic sheet, and the end face of the magnetic sheet becomes brittle. When the magnetic powder falls from the surface as well as when it is intended to obtain a soft magnetic sheet, the magnetic sheet becomes hard or the magnetic powder is a metal powder. As a result, flame retardancy may decrease. Further, if the magnetic powder is added in a large amount, the magnetic permeability is not improved. If the added amount is too large, a large number of voids may be formed in the magnetic sheet and the magnetic permeability may be lowered. That is, there is an optimum range for the amount of magnetic powder added. The weight of the magnetic powder in the magnetic sheet is preferably 70 to 90 wt%.

  When the content of at least one of the melamine cyanurate containing silicon atoms and the melamine cyanurate containing the carboxylic acid amide is less than 35 parts by mass, flame retardancy may not be sufficiently obtained, and 100 masses. When exceeding the part, the total amount of the magnetic powder and the flame retardant with respect to the binder becomes large, it becomes difficult to keep the magnetic powder and the flame retardant together by the binder, and in the magnetic sheet The content ratio of the magnetic powder may decrease, and the magnetic permeability may decrease.

--- Carbon fiber--
The magnetic layer preferably further contains carbon fiber. In this case, the noise suppression effect is improved. In addition, by combining the carbon fiber and the melamine cyanurate containing the silicon atom or the melamine cyanurate containing the carboxylic acid amide, a halogen-free and high flame retardancy can be achieved without containing the red phosphorus. Can do.
Here, the principle of noise energy attenuation is that incident electromagnetic wave energy is converted into thermal energy inside an electromagnetic wave suppression body such as a ferrite core or an electromagnetic wave suppression sheet formed by mixing magnetic powder with resin. Is. The mechanism of thermal energy conversion is mainly classified into three types of “conductivity”, “dielectric loss”, and “magnetic loss”, and the electromagnetic wave absorption energy P (W / m ³ ) per unit volume at this time. Is represented by the following formula (2) using the electrolysis E, the magnetic field H, and the frequency f. Here, in the following formula (2), the first term represents the conductive loss, the second term represents the dielectric loss, and the third term represents the magnetic loss.
P = 1 / 2σ | E | ² + πfε ″ | E | ² + πfμ | H | ² Formula (2)
In the formula (2), σ represents conductivity. ε represents a complex dielectric constant, and ε = ε′−jε ″. μ represents a complex magnetic permittivity, and μ = μ′−jμ ″.
When the carbon fiber is blended in the magnetic layer, the conductivity σ in the formula (2) is increased due to the effect of the filler of the carbon fiber. As a result, the P (electromagnetic wave absorption energy) is increased and noise is increased. The suppression effect is improved.
When the conductivity σ increases, the magnetic layer has conductivity, so that the use of the magnetic sheet may be limited. However, in the magnetic sheet of the present invention, the magnetic layer and the concavo-convex forming layer However, the noise suppression effect can be improved while the surface (unevenness forming layer) of the magnetic sheet is insulative.

There is no restriction | limiting in particular as said carbon fiber, Although a commercial item may be used and what was synthesize | combined suitably, As said commercial item, pitch-type carbon fiber ("Rahima R-A301") is sufficient, for example. Preferably made by Teijin) (fiber diameter 8 μm, fiber length 200 μm, specific gravity 2.2 g / cc).
There is no restriction | limiting in particular as content of the said carbon fiber, Although it can select suitably according to the objective, 5-200 mass parts is preferable with respect to 100 mass parts of said binders.
When the content is less than 5 parts by mass, the effect of noise suppression and flame retardancy may be reduced, and when the content exceeds 200 parts by mass, it may be difficult to mix at the time of preparing the magnetic composition.

-Other ingredients-
The other components are not particularly limited as long as they do not impair the function of the magnetic layer, and can be appropriately selected from known various additives according to the purpose.
A solvent may be added for the purpose of improving the coating properties of the magnetic composition (prepared by adding the magnetic powder and the flame retardant to the binder) when forming the magnetic layer. Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol; methyl acetate, ethyl acetate, propyl acetate, butyl acetate, Esters such as ethyl lactate and ethyl glycol acetate; ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane; aromatic hydrocarbon compounds such as benzene, toluene and xylene; methylene chloride and ethylene chloride Carbon tetrachloride, chloroform, halogenated hydrocarbon compounds such as chlorobenzene; and the like. These may be used individually by 1 type and may use 2 or more types together. In addition, various additives such as a dispersant, a stabilizer, a lubricant, a silane or titanate coupling agent, a filler, a plasticizer, and an anti-aging agent may be added as necessary.

There is no restriction | limiting in particular as thickness of the said magnetic layer, Although it can select suitably according to the objective, Thickness is preferable at the point from which a high magnetic permeability is obtained, and 25-500 micrometers is preferable.
When the thickness is less than 25 μm, the magnetic permeability is low, and when the thickness exceeds 500 μm, it is not suitable for a narrow part and does not follow the recent trend of downsizing of electronic devices, and the influence of the thickness on the magnetic permeability. May become smaller. When the thickness is 70 μm or less, the magnetic permeability tends to decrease rapidly.

-Concavity and convexity formation layer-
The unevenness forming layer has a function of peeling the magnetic sheet from a member in contact with the magnetic sheet, for example, in an electronic device when the magnetic sheet of the present invention is used.
The unevenness forming layer needs to have flame retardancy. Since the magnetic layer and the concavo-convex forming layer are integrated, if the concavo-convex forming layer has flame retardancy, even if the content of the flame retardant in the magnetic layer is reduced, the entire magnetic sheet Therefore, the magnetic properties of the magnetic sheet can be improved.
The flame retardancy can be evaluated by, for example, a UL94VTM test and a UL94V test (flammability test of plastic materials for equipment parts) as a combustion test.
The UL94VTM test is a method of evaluating flame retardance from the afterflame time after holding a film test piece wound in a cylindrical shape vertically and indirectly burning the flame of a burner for 3 seconds. The UL94V test is a method for evaluating the flame retardancy from the after-flame time after the flame of the burner is indirectly fired for 10 seconds on a test piece of a predetermined size held vertically. The evaluation results of these tests are divided into the following classes.
The said uneven | corrugated formation layer in the said magnetic sheet of this invention needs to have a flame retardance more than VTM-0 or V-1.
-Evaluation class-
VTM-0, V-0: The after flame time of each sample is 10 seconds or less, and the total after flame time of 5 samples is 50 seconds or less.
VTM-1, V-1: The after flame time of each sample is 30 seconds or less, and the total after flame time of five samples is 250 seconds or less.
VTM-2, V-2: Burning time is the same as VTM-1 or V-1, but there are flammable drops.
NG: Low flame retardancy and does not conform to UL94VTM or UL94V standards.
Here, the “residual flame time” means the length of time that the test piece continues to burn in flame after the ignition source is moved away.

The unevenness forming layer needs to have a Beck smoothness of 20 seconds / mL or less.
When the Beck smoothness is 20 seconds / mL or less, it is advantageous in that the slipperiness of the surface of the unevenness forming layer is excellent and the peeling effect from the member in contact with the magnetic sheet becomes remarkable.
The Beck smoothness is represented by the time required for a certain amount of air to pass through the uneven surface of a sheet-like member such as paper or cloth. The greater the degree of unevenness on the surface of the sheet-like member, the smaller the Beck smoothness means that it is excellent in so-called “slidability”.
The Beck smoothness can be measured using, for example, a Beck smoothness tester (manufactured by Tester Sangyo Co., Ltd.).

There is no restriction | limiting in particular about the structure, thickness, and material (material) as said uneven | corrugated formation layer, According to the objective, it can select suitably.
The structure may be a single layer structure or a laminated structure.
The thickness is preferably 2 to 100 μm.
When the thickness is less than 2 μm, workability may be deteriorated. When the thickness is more than 100 μm, heat is not easily transmitted to the magnetic layer at the time of hot pressing, and reliability may be lowered.
Examples of the material include synthetic resins, and for example, polyethylene terephthalate (PET) is preferable.

Although the said uneven | corrugated formation layer may be a commercial item and may be produced suitably, as said commercial item, for example, PET ("Lumirror ZV10"; which does not contain a halogen-type and phosphorus-type compound; Examples include PET manufactured by Toray Industries, Inc. (ULTM VTM test, VTM-0), and halogen-free and phosphorus-free compounds ("Lumirror ZV30"; manufactured by Toray Industries, Inc., UL94 VTM test, VTM-0). These are preferable in that they contain no halogen-based or phosphorus-based compounds, are halogen-free, and have flame retardancy.
As the unevenness forming layer, a layer on which characters are printed may be used. The printed surface of the character may be a surface in contact with the magnetic layer, or a surface not in contact with the magnetic layer (opposite surface).
Moreover, the said uneven | corrugated formation layer may be half-cut. In this case, the handleability when wound and used is good.

−Use−
The method of using the magnetic sheet of the present invention is not particularly limited and can be appropriately selected depending on the purpose. For example, the magnetic sheet is cut into a desired size and is used as a noise source for electronic equipment. In addition, the magnetic layer side can be disposed close to each other.

-Application-
The magnetic sheet of the present invention is suitably used for electromagnetic noise suppressors, radio wave absorbers, magnetic shield materials, electronic devices having IC tag functions such as RFID (cell phones with RFID function, etc.), non-contact IC cards, and the like. be able to.

Since the magnetic sheet of the present invention has the concavo-convex forming layer, when a high degree of insulation is required, or when it is used under a design (narrow site) in contact with other electronic components. Is preferred. In addition, since the magnetic powder in the magnetic layer is a metal, even when mixed with the binder, the surface resistance value is as low as 0.01 to 1 MΩ / □, and when a flame retardant is added, Since the surface resistance value tends to decrease, the magnetic sheet having flame retardancy preferably has the unevenness forming layer.
Due to the presence of the unevenness forming layer, the magnetic powder can be prevented from falling off from the surface of the magnetic layer. Further, since the unevenness forming layer is bonded to one surface of the magnetic layer, the moisture absorption area in the magnetic layer is narrowed, and the reliability is improved.
Further, the surface of the concavo-convex forming layer has concavo-convex portions and is excellent in slipperiness, and therefore can be suitably used for a battery pack portion of a mobile phone. In this case, even if the battery pack expands due to heat generation of the lithium battery due to repeated charging, adhesion with the battery pack is suppressed by the unevenness forming layer, so the open / close failure of the battery pack lid is improved. Is done.
When the concave / convex transfer layer is not transferred to the concave / convex forming layer, scratches are formed on the surface by opening and closing the lid of the battery pack, resulting in a poor appearance. If unevenness is formed on the unevenness forming layer by the unevenness transfer, there is an advantage that no scratches are formed on the unevenness forming layer.

Since the magnetic sheet of the present invention has a Beck smoothness of 20 seconds / mL or less, the slipperiness of the surface of the unevenness forming layer is excellent.
Further, the magnetic sheet of the present invention does not have an adhesive layer, unlike a conventional magnetic sheet. For this reason, it is possible to prevent the failure of the electronic device due to the leakage of the adhesive, which occurs when the electronic device is used at a high temperature. Moreover, since the thickness of the magnetic layer can be increased by the thickness of the adhesive layer as compared with the conventional magnetic sheet, the specific gravity is large and an excellent noise suppression effect is exhibited.
In the magnetic sheet of the present invention, the unevenness forming layer has flame retardancy, and the magnetic layer contains melamine cyanurate containing silicon atoms and melamine shear containing the carboxylic acid amide as the flame retardant. Since it contains at least one of nurate, it has high flame retardancy, is halogen-free and has a low environmental impact.
Here, the flame retardancy of the magnetic sheet of the present invention preferably has an evaluation of V-1 or higher in the UL94V test. The details of the UL94V test and its evaluation class are as described in the above-described evaluation of flame retardancy of the unevenness forming layer.

  There is no restriction | limiting in particular as the manufacturing method of the said magnetic sheet of this invention, Although it can select suitably according to the objective, It can manufacture suitably with the manufacturing method of the magnetic sheet of the following this invention.

(Magnetic sheet manufacturing method)
The method for producing a magnetic sheet of the present invention includes at least a magnetic layer forming step and a shape transfer step, and further includes other steps appropriately selected as necessary.

<Magnetic layer formation process>
The magnetic layer forming step is a step of forming a magnetic layer by molding a magnetic composition prepared by adding magnetic powder and a flame retardant to a binder.
The details of the binder, the magnetic powder, and the flame retardant are as described above. However, the binder preferably includes at least the thermosetting organic resin, and is described below before the hot press described later. Is preferably in an uncured state. Here, if the curing proceeds before the hot pressing, the magnetic layer is not sufficiently compressed and the magnetic permeability cannot be increased. In addition, when the hardened magnetic layer is compressed, strain remains, and when it is repeatedly exposed in a room temperature, high temperature or high temperature and high humidity environment, the thickness changes or the magnetic properties decrease. Or On the other hand, when the binder before the heating press is in an uncured state, the occurrence of these problems is suppressed.

The magnetic composition can be prepared by adding the magnetic powder and the flame retardant to the binder and mixing them.
The magnetic composition can be formed by, for example, applying the magnetic composition on a substrate and drying it.
There is no restriction | limiting in particular as said base material, Although it can select suitably according to the objective, The polyester film (peeling PET) by which peeling processing was performed etc. at the point which can peel the formed said magnetic layer easily. Are preferable.
Further, as the base material, matte PET, unpeeled PET, non-silicone peeled PET (the surface on which the magnetic layer is formed is not peeled), silicone peeled PET (magnetic layer is formed) The surface is not peeled), and halogen-free and flame-retardant PET may be used.
Through the above steps, the magnetic composition is molded to form the magnetic layer.

<Shape transfer process>
In the shape transfer step, an unevenness forming layer and a transfer material are laminated and arranged in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer, and then heated and pressed to thereby form the surface shape of the transfer material. Is transferred to the surface of the concavo-convex formation layer and the magnetic layer, and the concavo-convex formation layer and the magnetic layer are joined together.

-Concavity and convexity formation layer-
There is no restriction | limiting in particular about the structure, thickness, and material (material) as said uneven | corrugated formation layer, According to the objective, it can select suitably, These details are as above-mentioned.

The surface state of the unevenness forming layer is not particularly limited, and one surface in the thickness direction may be subjected to surface treatment or may not be subjected to any surface treatment. It is preferable that a release treatment without using a silicone resin is performed. In these cases, the slipperiness is improved as compared with those not subjected to any surface treatment. In the case of these surface treatments, since the silicone resin is not used, the silicone oligomer does not bleed out in a high temperature or high temperature and high humidity environment, and is suitable for use inside an electronic device.
The mat treatment is not particularly limited as long as the surface of the unevenness forming layer can be roughened, and can be selected according to the purpose. For example, sand mat treatment, chemical mat treatment, surface embossing treatment Etc. By these treatments, unevenness is formed on the surface of the unevenness forming layer, and slipperiness is improved.

The unevenness forming layer preferably has flame retardancy, and is preferably VTM-0 in the UL94VTM test or V-1 or more in the UL94V test.
The details of the UL94VTM test, the UL94V test, and their evaluation classes are as described above.

It is preferable that the unevenness forming layer has a Beck smoothness of 200 seconds / mL or less before heating press described later.
When the Beck smoothness before the heat press exceeds 200 seconds / mL, the Beck smoothness after the heat press may be adversely affected.
The details of the Beck smoothness are as described above.

-Transfer material-
The transfer material is not particularly limited in its structure, thickness, and material (material), and can be appropriately selected according to the purpose. However, the transfer material has irregularities on the surface and has good air permeability. Is preferred. In this case, when the unevenness on the surface of the transfer material is transferred to the unevenness forming layer, the unevenness is formed on the surface of the unevenness forming layer, the Beck smoothness of the unevenness forming layer is lowered, and slipperiness is reduced. improves.
The degree of unevenness on the surface of the transfer material can be evaluated by the magnitude of the Beck smoothness, and the smaller the Beck smoothness, the greater the degree of unevenness.

The structure may be a single layer structure or a laminated structure.
The thickness is preferably 25 to 200 μm.
When the thickness is less than 25 μm, a magnetic sheet with low Beck smoothness may not be obtained. When the thickness exceeds 200 μm, heat is not easily transmitted to the magnetic layer during the hot pressing, and reliability is reduced. Sometimes.
Examples of the material include paper, synthetic fiber, and natural fiber.

  The transfer material may be a commercially available product or an appropriately prepared material. Examples of the commercially available product include high-quality paper (“OK Prince Quality 70”; manufactured by Oji Paper Co., Ltd.) Beck smoothness 6.2 seconds / mL), cushion paper (“TF190”; manufactured by Toyo Fiber Co., Ltd., Beck smoothness 1.7 seconds / mL), nylon mesh (“N-NO.110S”; Tokyo Screen ( Co., Ltd., Beck smoothness less than 0.1 sec / mL), cotton ("Kanakin No. 3"; manufactured by Japan Standards Association, Beck smoothness less than 0.1 sec / mL), base paper for adhesive ("SO base paper") 18G "; manufactured by Daifuku Paper Co., Ltd., Beck smoothness less than 0.1 second / mL), double-sided release paper (" 100 GVW (high smooth surface) "; manufactured by Oji Paper Co., Ltd., Beck smoothness 146 seconds / mL) Double-sided release paper ("100GVW (low smooth surface)"; Oji Paper Ltd.), Beck smoothness of 66 sec / mL), and the like.

-Lamination arrangement-
The stacking method is not particularly limited as long as the unevenness forming layer and the transfer material are stacked in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer. The release layer and the transfer material are preferably further laminated in this order from the magnetic layer side on the other surface in the thickness direction of the magnetic layer. By interposing the release layer, the other surface of the magnetic layer is protected during the heat press described later to prevent adhesion with the transfer material, and after the heat press, the transfer material is removed from the release layer. It can be easily peeled from the magnetic layer together with the layer. Further, the surface shape of the transfer material is also transferred to the surface of the magnetic layer located on the release layer side. At this time, bubbles present in the magnetic composition in the magnetic layer are easily removed. The reliability of the magnetic sheet is improved. When the transfer material on the release layer side is not used, the magnetic permeability of the magnetic sheet can be improved.

  The release layer is not particularly limited as long as it has a function of preventing adhesion between the other surface in the thickness direction of the magnetic layer and the transfer material during the hot pressing, and is appropriately selected according to the purpose. However, a polyester film (peeled PET) having a surface subjected to a peeling treatment is preferable in that it can be easily peeled off from the magnetic layer after the hot pressing.

-Heating press-
The heating press method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the magnetic layer, the concavo-convex forming layer, and the transfer material are used as a laminate, and these are laminated on both sides by a laminator or a press. It can be carried out by sandwiching between and heating and pressurizing.
The surface shape (uneven shape) of the transfer material is transferred to the surface of the unevenness forming layer and the magnetic layer by the heating press, and the unevenness forming layer and the magnetic material can be transferred without using an adhesive or the like. The layers are joined directly.

  The conditions for the heating press are not particularly limited and may be appropriately selected depending on the purpose. The press temperature is preferably, for example, 80 to 190 ° C. The press pressure is preferably, for example, 5 to 20 MPa. The pressing time is preferably 1 to 20 minutes, for example.

Moreover, as the Beck smoothness of the said uneven | corrugated formation layer after the said heat press, 20 second / mL or less is preferable.
When the Beck smoothness exceeds 20 seconds / mL, the slipperiness of the surface of the unevenness forming layer is inferior, and adhesion between the magnetic sheet and a member in contact therewith may occur.

Through the above steps, the surface shape of the transfer material is transferred to the surfaces of the unevenness forming layer and the magnetic layer, and the unevenness forming layer and the magnetic layer are joined. As a result, a magnetic sheet having the magnetic layer and the unevenness forming layer is obtained.
In the magnetic sheet thus obtained, the surface shape of the transfer material (unevenness on the surface) is transferred to the surface of the concavo-convex forming layer and is roughened, so the Beck smoothness is low, Excellent slipperiness.

According to the method for producing a magnetic sheet of the present invention, the surface shape of the transfer material is transferred to the surface of the concavo-convex forming layer and the magnetic layer by the heating press, so that the surface of the concavo-convex forming layer is roughened. As a result, the Beck smoothness decreases, and the slipperiness can be improved.
Therefore, the unevenness forming layer is not limited to the original Beck smoothness, the Beck smoothness of the unevenness forming layer can be adjusted to a desired level, and there is room for material selection of the unevenness forming layer. spread. In addition, the Beck smoothness can be easily adjusted.
In addition, since the bubbles contained in the magnetic layer are efficiently released by the shape transfer step, the flame retardance of the magnetic layer can be improved, and the magnetic layer and the concavo-convex forming layer can be improved. In the meantime, no bubbles remain, and even if the amount of the flame retardant is reduced, high flame retardancy can be obtained.
Further, since the unevenness forming layer and the magnetic layer are directly bonded by the heating press, it is not necessary to form an adhesive layer, and a magnetic sheet can be produced simply and efficiently at low cost. Since the unevenness forming layer and the magnetic layer are integrated by direct bonding, even if the magnetic sheet is wound and used, generation of powder falling is suppressed.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example at all.

Example 1
-Production of magnetic sheet-
First, 270 parts by mass of toluene and 120 parts by mass of ethyl acetate, 92 parts by mass of an acrylic resin having an epoxy group (“SG series”; manufactured by Nagase ChemteX Corporation) as the binder, epoxy resin (“Epicoat 1031S”) A resin composition was prepared by dissolving 8 parts by mass of Japan Epoxy Resin Co., Ltd. and 8 parts by mass of an epoxy curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Co., Ltd.). In addition to this, 900 parts by mass of flat magnetic powder (Fe—Si—Cr—Ni, “JEM-S”; manufactured by Mitsubishi Materials) as the magnetic powder, and melamine shear containing carboxylic acid amide as the flame retardant 90 parts by mass of nurate (melamine cyanurate surface-treated with lauric acid as the fatty acid, “MC-5F”; manufactured by Sakai Chemical Industry Co., Ltd., number average particle size 0.5 μm), and red phosphorus (“ST-100 "; Manufactured by Phosphor Chemical Co., Ltd.) 10 parts by mass were added and mixed to prepare a magnetic composition.
The obtained magnetic composition was applied onto a polyester film (peeled PET; corresponding to a later-described peelable layer 22) as the substrate, and dried in the range from room temperature to 115 ° C. Thus, the magnetic layer 10 was produced. The above is the magnetic layer forming step.

Next, as shown in FIG. 1A, the surface of the magnetic layer 10 that does not have the release PET (release layer 22) in the thickness direction has a flame-retardant layer 20 as a concavo-convex forming layer, and is halogen-based and phosphorus-based. Polyester film not containing a compound (“Lumirror ZV10”; manufactured by Toray Industries, Inc., thickness 40 μm, V94-0 in UL94VTM test, Beck smoothness 28.2 seconds / mL), and high-quality paper (“ OK Prince Fine Quality 70 ”; manufactured by Oji Paper Co., Ltd., thickness 100 μm, Beck smoothness 6.2 seconds / mL) was laminated from the magnetic layer 10 side so that the concavo-convex forming layer 20 and the transfer material 30 were in this order. .
Further, on the other surface in the thickness direction of the magnetic layer 10, the transfer material 30 is laminated on the release layer 22 (release PET (“38GS”; manufactured by Lintec, thickness 38 μm)) already laminated as the base material, A laminate 40 was formed.

Next, using a vacuum press (made by Kitagawa Seiki Co., Ltd.), press plates 50 from both sides of the laminate 40 as shown in FIG. 1B under the conditions of a press temperature of 170 ° C., a press time of 10 minutes, and a press pressure of 9 MPa. The surface shape of the transfer material 30 is transferred to the surfaces of the concavo-convex forming layer 20 and the magnetic layer 10, and the concavo-convex forming layer 20 and the magnetic layer 10 are joined together to form a magnetic layer having a thickness of 109 μm. 10 was formed. The above is the shape transfer step.
The laminated body 40 after the heat pressing was cut so as to have a sample size of 250 mm × 250 mm.
Thereafter, as shown in FIG. 1C, the transfer material 30 and the release layer 22 were peeled off from the concavo-convex forming layer 20 and the magnetic layer 10, respectively, to obtain a magnetic sheet 100 having a thickness of 149 μm.

<Confirmation of presence of carboxylic acid amide in melamine cyanurate>
The obtained magnetic sheet was immersed in toluene and then pulverized in a mortar, and the obtained pulverized product was dispersed in toluene. Next, the magnetic powder and the binder are separated by centrifugation, and each component in the binder is further separated and extracted. About MC-5F (manufactured by Sakai Chemical Industry) as the flame retardant, pyrolysis gas Analysis by chromatography (Py-GC-MS) was performed. The Py-GC-MS measurement data is shown in FIG. 2A. For comparison, as a melamine cyanurate (no surface treatment), Py-GC-MS measurement data of MC-20N (manufactured by Sakai Chemical Industry) is shown in FIG. 2B, and Py- of MC-40N (manufactured by Sakai Chemical Industry). The GC-MS measurement data is shown in FIG. 2C. From FIG. 2A to FIG. 2C, lauroylamide was detected only in the Py-GC-MS measurement data of MC-5F, and it was confirmed that the MC-5F contained a carboxylic acid amide.

  In addition, the magnetic powder extracted by the centrifugation was washed with toluene, and the supernatant of the obtained washing solution was collected, and toluene was distilled off under reduced pressure using an evaporator. Next, the residue (the concentrate of the toluene washing solution) was analyzed by infrared spectroscopy (IR). This IR measurement data is shown in FIG. 3A. From FIG. 3A, OH stretching vibration derived from a hydroxyl group was not observed. Then, when a library search was performed, as shown in FIG. 3B, it was found that the concentrate of the toluene washing solution was a glyceride (ester compound of glycerin and fatty acid) which is a kind of fatty acid ester. It was confirmed that no carboxylic acid amide was contained therein. In FIG. 3B, the solid line represents the concentrate of the toluene washing solution, and the broken line represents the library (glyceride).

(Example 2)
-Production of magnetic sheet-
In Example 1, a magnetic sheet was produced in the same manner as in Example 1 except that the composition of the binder was changed to the composition shown in Table 1.

(Example 3)
-Production of magnetic sheet-
In Example 1, the composition of the binder was changed to the composition shown in Table 1, and the unevenness forming layer 20 was made of a polyester film (“Lumirror ZV10”; A magnetic sheet was produced in the same manner as in Example 1 except that the thickness was 25 μm, and the thickness was changed to VTM-0 and Beck smoothness of 40.6 seconds / mL in the UL94 VTM test.

Example 4
-Production of magnetic sheet-
A magnetic sheet was produced in the same manner as in Example 1 except that the blending amount of the magnetic powder and the composition of the binder were changed as shown in Table 1 in Example 1.

(Example 5)
-Production of magnetic sheet-
In Example 1, the magnetic powder was replaced with 850 parts by mass of Fe—Si—Al (“EMS-10”; manufactured by Mitsubishi Materials), and the composition of the binder and the blending amount of the flame retardant are shown in Table 1. A magnetic sheet was produced in the same manner as in Example 1 except that the above was changed.

(Example 6)
-Production of magnetic sheet-
In Example 4, the blending amount of the magnetic powder was changed as shown in Table 1, and the melamine cyanurate containing a carboxylic acid amide as the flame retardant was replaced with a melamine cyanurate containing a silicon atom (using a silicon compound). A magnetic sheet was produced in the same manner as in Example 4, except that the surface-treated melamine cyanurate, “MC-5S” (manufactured by Sakai Chemical Industry), was used.

<Confirmation of the presence of silicon atoms in melamine cyanurate>
The obtained magnetic sheet was immersed in toluene and then pulverized in a mortar, and the obtained pulverized product was dispersed in toluene. Subsequently, the magnetic powder and the binder are separated by centrifugation, and each component in the binder is further separated and extracted. With respect to MC-5S (manufactured by Sakai Chemical Industry) as the flame retardant, fluorescent X-ray Analysis (XRF) was performed. The XRF measurement data is shown in FIG. 4A. For comparison, as melamine cyanurate (no surface treatment), XRF measurement data of MC-20N (manufactured by Sakai Chemical Industry) is shown in FIG. 4B, and XRF measurement data of MC-40N (manufactured by Sakai Chemical Industry) is shown in FIG. 4C. Respectively. 4A to 4C, silicon atoms were detected only in the XRF measurement data of MC-5S, and it was confirmed that MC-5S contained silicon atoms.

(Examples 7 to 8)
-Production of magnetic sheet-
In Example 6, the composition of the flame retardant was changed as shown in Table 2, except that melamine cyanurate containing a carboxylic acid amide and melamine cyanurate containing a silicon atom were used in the same manner as in Example 6. A magnetic sheet was prepared.

(Examples 9 to 10)
-Production of magnetic sheet-
In Example 5, a magnetic sheet was produced in the same manner as in Example 5 except that the blending amounts of the magnetic powder and the flame retardant were changed as shown in Table 2.

(Examples 11 to 18)
-Production of magnetic sheet-
In Example 2, carbon fiber (pitch-based carbon fiber, “Lahema R-A301”; manufactured by Teijin, fiber diameter of 8 μm, fiber length of 200 μm, specific gravity of 2.2 g / cc) is added in the amounts shown in Tables 2 to 3. And the magnetic sheet was produced like Example 2 except having changed the composition of the said binder and the said flame retardant as shown in Tables 2-3.

(Comparative Example 1)
-Production of magnetic sheet-
In Example 1, the composition of the binder was changed to the composition shown in Table 4, and the concavo-convex forming layer 20 was changed to PET (“XR30”; manufactured by Toray Sehan) having a thickness of 4.5 μm and not subjected to peeling treatment. Produced a magnetic sheet in the same manner as in Example 1.

(Comparative Example 2)
-Production of magnetic sheet-
In Example 1, except that the composition of the binder was changed to the composition shown in Table 4, and the concavo-convex forming layer 20 was replaced with 25 μm-thick PET (“emblet”; manufactured by Unitika) having a thickness of 25 μm. A magnetic sheet was produced in the same manner as in Example 1.

(Comparative Example 3)
-Production of magnetic sheet-
In Example 1, the composition of the binder was changed to the composition shown in Table 4, and the unevenness forming layer 20 was replaced with PET (“25GS”; manufactured by Lintec) subjected to silicone peeling treatment. In the same manner as in Example 1, a magnetic sheet was produced.

(Comparative Example 4)
-Production of magnetic sheet-
In Example 1, the composition of the binder was changed to the composition shown in Table 4, and the unevenness forming layer 20 was replaced with non-silicone release-treated PET (“Fluorogen RL”; manufactured by Mitsubishi Plastics). In the same manner, a magnetic sheet was produced.

(Comparative Example 5)
-Production of magnetic sheet-
In Example 9, the compounding amount of red phosphorus was changed as shown in Table 4, and 45 parts by mass of melamine cyanurate containing the carboxylic acid amide as the flame retardant was subjected to surface treatment with polyvinyl alcohol. A magnetic sheet was produced in the same manner as in Example 9 except that 90 parts by mass of nurate (“MC610”; manufactured by Nissan Chemical Industries, number average particle size 1.1 μm) was used.

(Comparative Example 6)
-Production of magnetic sheet-
In Example 9, the compounding amount of red phosphorus was changed as shown in Table 5, and 45 parts by mass of the melamine cyanurate containing the carboxylic acid amide as the flame retardant was treated with melamine cyanurate (untreated). “MC6000” (manufactured by Nissan Chemical Industries, Ltd., number average particle size 2.2 μm) A magnetic sheet was produced in the same manner as in Example 9, except that 90 parts by mass was used.

(Comparative Example 7)
-Production of magnetic sheet-
In Example 9, the compounding amount of red phosphorus was changed as shown in Table 5, and 45 parts by mass of melamine cyanurate containing the carboxylic acid amide as the flame retardant was added to melamine polyphosphate (“PMP100”; Nissan) A magnetic sheet was produced in the same manner as in Example 9 except that the amount was changed to 90 parts by mass.

(Comparative Example 8)
-Production of magnetic sheet-
In Example 9, the compounding amount of red phosphorus was changed as shown in Table 5, and 45 parts by mass of melamine cyanurate containing the carboxylic acid amide as the flame retardant was added to magnesium hydroxide (“MGZ-3”). A magnetic sheet was prepared in the same manner as in Example 9, except that 90 parts by mass (manufactured by Sakai Chemical Industry Co., Ltd., number average particle size 0.1 μm) was used.

(Comparative Example 9)
-Production of magnetic sheet-
In Example 9, the compounding amount of red phosphorus was changed as shown in Table 5, and 45 parts by mass of melamine cyanurate containing the carboxylic acid amide as the flame retardant was added to ammonium polyphosphate (“AP462”; Clariant). (Manufactured) A magnetic sheet was produced in the same manner as in Example 9 except that 90 parts by mass was used.

(Comparative Example 10)
-Production of magnetic sheet-
In the same manner as in Example 1, a magnetic layer was formed on the substrate (the release layer), and this was heated using a heating press (“KVHC-PRESS”; manufactured by Kitagawa Seiki Co., Ltd.) at a press temperature of 170 ° C. The magnetic layer was cured by pressing at a pressing pressure of 9 MPa for 10 minutes to form a 65 μm magnetic layer.
Next, an adhesive (“No. 5601”; manufactured by Nitto Denko Corporation) was applied to the surface of the cured magnetic layer to form an adhesive layer having a thickness of 10 μm. A polyester film containing no flame and phosphorus compounds and having flame retardancy (“Lumirror ZV10”, manufactured by Toray Industries, Inc., thickness 40 μm, Beck smoothness 28.2 sec / mL) was laminated.
Next, similarly to Example 1, after laminating the transfer material on the concavo-convex forming layer and the release layer, the magnetic layer and the concavo-convex were formed using a hand roller (manufactured by Sony Chemical & Information Device). The transfer layer and the release layer were peeled off to obtain a magnetic sheet having a thickness of 86 μm.

  For the magnetic sheets obtained in Examples 1 to 18 and Comparative Examples 1 to 10, measurement of the Beck smoothness on the surface of the unevenness forming layer and evaluation of the appearance, evaluation of flame retardancy by a flammability test, in a high temperature and high humidity environment A reliability test (measurement of the rate of change in thickness of the magnetic layer), evaluation of the presence or absence of powder from the surface of the magnetic sheet before and after the reliability test, and evaluation of LOSS characteristics were performed based on the following methods. The results are shown in Tables 1-5.

[Beck smoothness]
The Beck smoothness on the surface of the unevenness forming layer was measured using a Beck type smoothness tester (manufactured by Tester Sangyo Co., Ltd.) when 1 cc of air was passed.

[Appearance evaluation]
The appearance of the surface of the unevenness forming layer was visually observed and evaluated based on the following criteria.
-Evaluation criteria-
○: No scratches are visually confirmed on the surface of the concavo-convex forming layer, and no air is present between the concavo-convex forming layer and the magnetic layer. ×: Scratches are visually confirmed on the surface of the concavo-convex forming layer, and the concavo-convex forming layer and the magnetic layer. Air is in between

[Combustion test]
In the combustion test, a UL94V test (flammability test of plastic material for equipment parts) was performed on the magnetic sheet composed of the magnetic layer and the unevenness forming layer. The UL94V test is a method for evaluating flame retardancy from the afterflame time after indirect flame is burned for 10 seconds on a test piece of a predetermined size held vertically, and the evaluation results are in the class shown below. Divided.

-Evaluation class-
V-0: The after flame time of each sample was 10 seconds or less, and the total after flame time of 5 samples was 50 seconds or less.
V-1: The after flame time of each sample is 30 seconds or less, and the total after flame time of five samples is 250 seconds or less.
V-2: The combustion time is the same as V-1, but there are flammable drops.
NG: Low flame retardancy and does not conform to UL94V standard.
Here, the “residual flame time” means the length of time that the test piece continues to burn in flame after the ignition source is moved away.

〔Reliability test〕
-Change in thickness of magnetic layer-
First, the thickness of the magnetic sheet was measured, and the thickness of the uneven layer was subtracted from the thickness of the magnetic sheet to calculate the thickness of only the magnetic layer.
Next, the magnetic sheet was placed in an oven, heated at 85 ° C./60% for 96 hours, and taken out of the oven. The thickness of the magnetic layer after heating was measured by measuring the thickness of the magnetic sheet after heating, subtracting the thickness of the unevenness forming layer from the thickness of the magnetic sheet, and calculating the thickness of only the magnetic layer. .

[Food fall]
The powder fall is observed by observing whether the magnetic powder falls from the surface of the magnetic sheet when the magnetic sheet surface is touched before and after the reliability test described above, and the magnetic powder adheres to the hand. evaluated.

[Measurement method of LOSS characteristics (transmission loss)]
A microstrip line with impedance Z = 50Ω was used for measurement of transmission loss. The microstrip line is a method for measuring transmission loss of nearby noise, which is widely used because of its structure suitable for mounting surface mount components and ease of fabrication. The shape of the microstrip line used is shown in FIG. The transmission loss is measured by providing a linear conductor path on the surface of the insulator substrate and placing a magnetic sheet on the conductor path. Both ends of the conductor path are connected to a network analyzer. Then, with respect to the incident wave indicated by the arrow, the reflection amount (dB) and the transmission amount (dB) from the mounting portion of the electromagnetic wave absorbing material are measured, and the difference between them is the loss amount, and the transmission loss (absorption rate) is (Incident amount = reflection S11 + loss + transmission S21). Specifically, a known incident amount was incident, and the reflection amount S11 and the transmission amount S21 were measured and measured to obtain a loss amount.
The transmission loss of the microstrip line increases as the thickness of the magnetic sheet increases. In general, a magnetic sheet having a small thickness and a high transmission loss is desired.

From the results of Tables 1 to 5, as the flame retardant, at least one of a melamine cyanurate containing a silicon atom and a melamine cyanurate containing a carboxylic acid amide is used. The magnetic sheets used in Examples 1 to 18 have high flame retardancy, and do not fall off from the surface of the magnetic sheet before and after the reliability test in a high-temperature and high-humidity environment, and also have dimensional stability. It was found to be good. Moreover, it turned out that the high noise suppression effect is shown from the result of LOSS characteristic evaluation. Furthermore, the appearance of the surface of the unevenness forming layer was also good.
In addition, in the magnetic sheets of Examples 11 to 18 containing the carbon fiber, the noise suppression effect is high, and even if the content of the flame retardant is small, the flame retardancy is high. Since 100 parts by mass of carbon fiber was included and 200 parts by mass of carbon fiber was included in Example 18, an evaluation result of “V-0” could be obtained without containing red phosphorus.

On the other hand, in Comparative Examples 1 to 4, since the unevenness forming layer does not have flame retardancy, the magnetic layer contains either melamine cyanurate containing silicon atoms or melamine cyanurate containing carboxylic acid amide. However, it was found that the evaluation results of flame retardancy were bad.
Moreover, in Comparative Examples 5-9, neither the melamine cyanurate containing a silicon atom nor the melamine cyanurate containing a carboxylic acid amide was contained as the flame retardant. It was. Here, in Comparative Example 5, melamine cyanurate was surface-treated with polyvinyl alcohol, but the evaluation result of flame retardancy was “NG”, and melamine cyanurate was simply surface-treated. Thus, it was found that high flame retardancy cannot be obtained, and it is necessary to perform a surface treatment that imparts at least one of a silicon atom and a carboxylic acid amide.
Moreover, in Comparative Example 10, since the adhesive layer was provided and the shape transfer step was not performed, air was present between the concavo-convex forming layer and the magnetic layer, causing a reduction in flame retardancy. Moreover, since the thickness of the said magnetic layer became thin by the thickness of the said adhesion layer, the noise suppression effect became low.

The magnetic sheet of the present invention is suitably used for, for example, an electromagnetic noise suppressor, a radio wave absorber, a magnetic shield material, an electronic device having an IC tag function such as an RFID (a mobile phone with an RFID function), a non-contact IC card, etc. can do.
The method for producing a magnetic sheet of the present invention is to easily and efficiently produce a magnetic sheet having excellent surface slipperiness, high flame retardancy and noise suppression effect, and having a small environmental load. Can do.

DESCRIPTION OF SYMBOLS 10 Magnetic layer 20 Concavity and convexity formation layer 22 Release layer 30 Transfer material 40 Laminate 50 Press plate 100 Magnetic sheet (present invention)

Claims (4)

Comprising a magnetic layer and a concavo-convex forming layer;
The magnetic layer contains at least a binder, magnetic powder, and a flame retardant, and the flame retardant contains at least one of melamine cyanurate containing silicon atoms and melamine cyanurate containing carboxylic acid amide,
The said uneven | corrugated formation layer has a flame retardance, and Beck smoothness is 20 second / mL or less, The magnetic sheet characterized by the above-mentioned.   The magnetic layer contains 700 parts by mass to 1,300 parts by mass of magnetic powder, 35 parts by mass to 100 parts by mass of a flame retardant, and the content of the magnetic powder in the magnetic layer with respect to 100 parts by mass of the binder. The magnetic sheet according to claim 1, wherein is 70 wt% to 90 wt%.   The magnetic sheet according to claim 1, further comprising carbon fibers in the magnetic layer. A magnetic layer forming step of forming a magnetic layer by molding a magnetic composition prepared by adding magnetic powder and a flame retardant to a binder;
After the concave / convex forming layer and the transfer material are stacked in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer, the surface shape of the transfer material is changed to the concave / convex forming layer by heat pressing. And transferring to the surface of the magnetic layer, and a shape transfer step of joining the unevenness forming layer and the magnetic layer;
A method for producing a magnetic sheet, comprising: